Artificial lung

ABSTRACT

An artificial lung includes a housing, a tubular hollow fiber membrane bundle contained in the housing and providing a multiplicity of hollow fiber membranes having a gas exchange function, a gas inflow port and a gas outflow port communicating with each other through hollow portions of the hollow fiber membranes, and a blood inflow port and a blood outflow port through which blood is distributed. The tubular hollow fiber membrane bundle has a cylindrical overall shape, and a filter member having a bubble-trapping function is provided on an outer peripheral portion of the tubular hollow fiber membrane bundle.

This application is a continuation of application Ser. No. 11/179,743filed on Jul. 13, 2005. This application is also based on and claimspriority under 35 U.S.C. §119 with respect to Japanese Application No.2004-216448 filed on Jul. 23, 2004, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to an artificial lung.

BACKGROUND DISCUSSION

Conventional artificial lungs include those having a hollow fibermembrane bundle. An example of such an artificial lung is described inJapanese Patent Laid-Open No. Hei 11-47268, corresponding to EuropeanApplication Publication No. 0 895 786.

This artificial lung includes a housing, a hollow fiber membrane bundle(hollow fiber membrane accumulation) contained in the housing, a bloodinflow port and a blood outflow port, and a gas inflow port and a gasoutflow port. In the event bubbles are present in the blood flowing invia the blood inflow port of the artificial lung having such aconfiguration, it is preferable that the bubbles are removed by thehollow fiber membrane bundle.

However, problems arise in that the bubbles are not sufficiently removedby the hollow fiber membrane bundle and might flow out to the bloodoutflow port together with the blood.

SUMMARY

According to one aspect of the present invention, an artificial lungincludes: a housing; a hollow fiber membrane bundle contained in thehousing and in which a multiplicity of hollow fiber membranes having agas exchanging function are accumulated; a gas inflow portion and a gasoutflow portion communicated with each other through the lumens of thehollow fiber membranes; and a blood inflow portion and a blood outflowportion in which blood flows. The hollow fiber membrane bundle has acylindrical overall shape. A bubble trapping filter member which isadapted to trap bubbles is provided at an outer peripheral portion ofthe hollow fiber membrane bundle or at an intermediate portion in thethickness direction of the hollow fiber membrane bundle.

Preferably, the filter member is provided in contact with an outerperipheral portion of the hollow fiber membrane bundle and coverssubstantially the entire part of the outer peripheral portion. In theartificial lung, a gap is preferably formed between the filter memberand the housing.

Preferably, the blood inflow portion has an inflow opening portionopening to the inner peripheral portion side of the hollow fibermembrane bundle, while the blood outflow portion has an outflow openingportion opening to the outer peripheral portion side of the hollow fibermembrane bundle, and the blood passes from the inner peripheral portionside to the outer peripheral portion side of the hollow fiber membranebundle.

The filter member may be hydrophilic. In addition, the filter member maybe mesh-like. The opening of the filter member is preferably not morethan 50 μm.

According to another aspect, an artificial lung comprises a housingcomprising a blood inflow port through which blood flows, a bloodoutflow port through which blood flows, a gas inflow port through whichflows gas and a gas outflow through which flows gas. A tubular hollowfiber membrane bundle is positioned in the housing and comprises aplurality of hollow fiber membranes, with the gas inflow portcommunicating with the hollow fiber membrane bundle and the gas outflowport communicating with the hollow fiber membrane bundle. A firstannular blood chamber is positioned radially inwardly of the hollowfiber membrane bundle and communicates with the blood inflow port, and asecond annular blood chamber is positioned radially outwardly of thehollow fiber membrane bundle and communicates with the blood outflowport. An annular bubble trapping filter member is positioned in thehousing between a circumferential inner surface of the housing and thefirst annular blood chamber to trap bubbles contained in blood in thehollow fiber membrane bundle.

The embodiments of the artificial lung described here are able torelatively securely trap bubbles present in the blood by the filtermember provided at the hollow fiber membrane bundle. It is thus possiblewith the artificial lung described here to relatively reliably preventthe bubbles from flowing out from the blood outflow portion.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The above and other features and characteristics of the artificial lungwill become more apparent from the following detailed descriptionconsidered together with the accompanying drawing figures in which likeelements are designated by like reference numerals.

FIG. 1 is a front view of an artificial lung according to a firstembodiment of the present invention.

FIG. 2 is a left side view of the artificial lung shown in FIG. 1.

FIG. 3 is a cross-sectional view along line A-A of FIG. 2.

FIG. 4 is a cross-sectional view along line B-B of FIG. 2.

FIG. 5 is a cross-sectional view along line C-C of FIG. 1.

FIG. 6 is a cross-sectional view of an artificial lung according to asecond embodiment of the present invention.

DETAILED DESCRIPTION

Referring generally to FIGS. 1-5, one embodiment of the artificial lung1 includes a tubular core 5, a tubular (cylindrical) hollow fibermembrane bundle 3 in which are accumulated a multiplicity of gasexchange hollow fiber membranes 3 a, which are adapted to perform a gasexchange function, wound around the outer surface of the tubular core 5,a housing for containing the tubular hollow fiber membrane bundle 3therein, a gas inflow portion and a gas outflow portion communicatingwith each other through the inside (lumen) of the hollow fiber membranes3 a, a blood inflow portion and a blood outflow portion forcommunication between the exterior of the hollow fiber membranes 3 andthe inside of the housing, and a filter member 6 provided at the tubularhollow fiber membrane bundle 3. The tubular hollow fiber membrane bundle3 has a structure in which hollow fiber membrane layers (hollow fibermembranes 3 a) spread on the outer peripheral surface of the tubularcore 5 are stacked in a multi-layer form, i.e., stacked or layered in aspiral form, or taken up into a reel form, with the tubular core as acore. Further, the hollow fiber membrane layers are so configured thatan intersection portion 3 b where the hollow fiber membranes 3 aintersect each other is provided in the vicinity of the center in thelongitudinal direction of the tubular core 5, with the intersectionportions 3 b being located at different positions so that oneintersection portion 3 b is not stacked directly on another intersectionportion 3 b, or a direct stacking of one intersection portion 3 b andanother intersection portion 3 b does not occur.

The artificial lung 1 includes the housing 2, an artificial lung unitcontained in the housing 2, and a tubular heat exchanger unit containedin the artificial lung unit so that the artificial lung is a heatexchange function-incorporating artificial lung.

The artificial lung 1 comprises: the artificial lung unit which includesthe tubular core 5, the tubular hollow fiber membrane bundle 3 having amultiplicity of gas exchange hollow fiber membranes wound around theoutside surface of the tubular core 5, and a filter member 6; thetubular heat exchanger unit contained in the tubular core 5; and thehousing 2 containing the artificial lung unit and the tubular heatexchanger unit therein. The outwardly facing surface of the tubular core5 is provided with a plurality of grooves 51 forming blood conduitsbetween the outside surface of the tubular core 5 and the inside surfaceof the tubular hollow fiber membrane bundle 3. The tubular core 5 isalso provided with a blood flow opening(s) 52 providing communicationbetween a first blood chamber 11, formed between the tubular core 5 andthe tubular heat exchanger unit, and the grooves 51.

The artificial lung 1 has a blood inflow port (blood inflow portion) 24communicating with the first blood chamber 11 (the inner peripheralportion side of the tubular hollow fiber membrane bundle 3) formedbetween the tubular core 5 and the tubular heat exchanger unit, and ablood outflow port (blood outflow portion) 25 communicating with asecond blood chamber 12 (the outer peripheral portion side of thetubular hollow fiber membrane bundle 3) formed between the outsidesurface of the tubular hollow fiber membranes and the inside surface ofthe housing 2.

In addition, the blood inflow port 24 is provided with an inflow openingportion 40 opening into the first blood chamber 11. This helps ensurethat blood from the blood inflow port 24 flows assuredly into the firstblood chamber 11. The blood in the first blood chamber 11 passes througha blood distribution opening(s) 52 and through an inner peripheralportion 15 of the tubular hollow fiber membrane bundle 3 into the inside16 of the tubular hollow fiber membrane bundle 3. In addition, the bloodwhich has flowed into the inside 16 of the tubular hollow fiber membranebundle 3 flows via an outer peripheral portion 17 of the tubular hollowfiber membrane bundle 3 into the second blood chamber 12.

In addition, the blood outflow port 25 is provided with an outflowopening portion 43 opening into the second blood chamber 12. This helpsensure that the blood in the second blood chamber 12 flows out to theblood outflow port 25 assuredly.

As shown in FIGS. 3 to 5, in the artificial lung 1, a tubular housingbody 21, the second blood chamber 12, the hollow fiber membrane bundle3, the tubular core 5 having the grooves 51, the first blood chamber 11,a tubular heat exchanger 31, tubular heat exchanger deformationrestraining portions 34, 35, and a tubular heating medium forming member32 are arranged or formed concentrically in this order from the outside.As shown in FIG. 1 and FIGS. 3 to 5, the housing 2 includes the tubularhousing body 21 having the blood outflow port 28; a first header 22having a gas inflow port (gas inflow portion) 26, a heating mediuminflow port 25 and a heating medium outflow port 29; and a second header23 having a gas outflow port (gas outflow portion) 27 and an insertionport for the blood inflow port 24 provided in the tubular core 5. Thefirst header 22 is provided at its inside surface with a heating mediumchamber forming member connection portion 22 a projecting in a tubularform, and a partition portion 22 b bisecting or dividing the inside ofthe heating medium chamber forming member connection portion 22 a. Inaddition, the second header 23 is provided at its inside surface with aheating medium chamber forming member connection portion 32 projectingin a tubular form. As shown in FIG. 4, a tubular heating medium chamberforming member 32 described later has an opening end side held by thefirst header 22 and a closed end side held by the second header 23.

The artificial lung unit includes the tubular core 5, the tubular hollowfiber membrane bundle 3 having a multiplicity of hollow fiber membraneswound around the outside surface of the tubular core 5, and the filtermember 6 provided on the outer peripheral portion 17 of the tubularhollow fiber membrane bundle 3.

As shown in FIGS. 3 to 5, the tubular core 5 is tubular in shape. Anannular plate-like projecting portion 55 extending on the inside with apredetermined width is formed at one end of the tubular core 5, and theblood inflow port 24 is formed at the outside surface of a flat surfaceportion of the annular plate-like projecting portion 55 in parallel tothe center axis of the tubular core 5 so as to project outwards. Theoutside surface of the tubular core 5 is provided with the multiplicityof grooves 51 forming blood conduits between the outside surface of thetubular core 5 and the inside surface of the tubular hollow fibermembrane bundle 3.

The tubular core 5 also has the blood distribution opening(s) 52providing communication between the grooves 51 and the first bloodchamber 11 which is formed between the tubular core 5 and the tubularheat exchanger unit. The tubular core 5 possesses an outside diameterthat is preferably about 20 to 100 mm, and an effective length (i.e.,the length of the portion not buried in the partition wall) ofpreferably about 10 to 730 mm. More specifically, the plurality ofgrooves 51 of the tubular core 5 are parallel to one another, but notcontinuous, and axially spaced apart over a range of the core exclusiveof both end portions. In addition, the portions between the axiallyadjacent grooves 51 are provided as annular ribs 53.

The grooves in the tubular core 5 are so formed as to be present oversubstantially the whole area of that portion of the hollow fibermembrane bundle which contributes to gas exchange (the effective length,or the portion not buried in the partition wall). As generally shown inFIG. 5, the tubular core 5 used here has a non-grooved portion 54 (of agenerally flat surface form) which is located substantially on anextension line of the blood inflow port 24 and extends substantiallyover the entirety of the grooved portion of the tubular core 5.Therefore, the grooves 51 and the ribs 53 of the tubular core 5 areformed as annular grooves 51 (arcuate grooves and annular ribs 53(arcuate ribs) having starting ends and finishing ends (i.e., thegrooves and ribs are not continuous). As mentioned, the non-groovedportion 54 of the core 5 extends substantially over the whole part(i.e., axial extent) of the grooved portion of the tubular core 5,whereby shape stability of the tubular hollow fiber membrane bundle 3provided at the outside surface of the tubular core 5 is enhanced.

However, it is to be understood that the non-grooved portion 54 is notindispensable, as the grooves 51 and the ribs 53 of the tubular core 5may be endless fully annular grooves 51 and endless fully annular ribs53, respectively.

The tubular core 5 is provided with the grooves 51 over substantiallythe entire range of the effective length (the portion not buried in thepartition wall) of the hollow fiber membrane bundle 3 so that it ispossible to disperse the blood to substantially the whole part of thehollow fiber membrane bundle 3, thus effectively utilizing substantiallythe whole part of the hollow fiber membranes and achieving a relativelyhigh gas exchange performance.

Further, the top of each of the ribs 53 formed between the grooves 51 ofthe tubular core 5 is preferably a generally flat surface, meaning thatthe top of each of the ribs is not pointed. With the ribs 53 thus formedas generally flat surfaces, shape stability of the tubular hollow fibermembrane bundle 3 formed on the outside surface of the tubular core 5 isenhanced.

As generally seen in FIG. 3, the cross-sectional shape of each of theribs 53 is a shape that narrows toward the top of the rib (i.e., in adirection toward the hollow fiber membrane bundle 3. The ribs may thuspossess a somewhat trapezoidal shape in cross-section). This helpsensure that the grooves 51 (blood conduits) are each broadened towardthe inside surface of the hollow fiber membrane bundle so that the bloodflows into the hollow fiber membrane bundle favorably.

In addition, the blood inflow port 24 is provided on the side of one endportion of the tubular core 5, and the blood distribution opening(s) 52is formed in a region opposed to a region obtained by extending thecenter line of the blood inflow port 24. This helps provide a relativelyuniform blood distribution in the first blood chamber 11 formed betweenthe tubular core 5 and the tubular heat exchanger unit, and can alsoenhance the heat exchange efficiency.

More specifically, as shown in FIG. 5, the non-grooved portion 54 iscircumferentially located substantially on the extension line of theblood inflow port 24 (i.e., the axis or center line of the blood inflowport 24 circumferentially coincides with the location of the non-groovedportions 54) and extends over substantially the entire axial extent ofthe grooved portion. The non-grooved portion 54 is a thinner portion(i.e., thinner in the radial direction) enabled by the absence of thegrooves, whereby a blood guide portion 56 circumferentially locatedsubstantially on the extension line of the blood inflow port 24 (on theaxial extension of the center line of the blood inflow port 24) isformed in the inside of the tubular core 5. The blood guide portion 56is larger in inside diameter than the grooved portions. With the bloodguide portion 56 thus provided, it is possible to cause the blood torelatively reliably flow into the whole part in the axial direction ofthe first blood chamber 11 formed between the tubular core and thetubular heat exchanger unit.

In this disclosed embodiment of the artificial lung, a plurality ofblood distribution openings 52 are provided in the tubular core 5 andare individually communicated with the plurality of annular grooves 51.The blood distribution openings 52 are circumferentially located in aregion or location that is opposed (diametrically opposed) to thenon-grooved portion 54 (blood guide portion 56). One of the ribs 53 ispresent between the adjacent openings 52.

As shown in FIG. 4, the hollow fiber membrane bundle 3 is wound aroundthe outside surface of the tubular core 5. The hollow fiber membranes 3a forming the hollow fiber membrane bundle 3 are sequentially woundaround the tubular core 5, as shown in FIG. 1, whereby the hollow fibermembrane layers spread on the outer peripheral surface of the tubularcore 5 are stacked in a multi-layer form, i.e., stacked in a spiral formor taken up into a reel form with the tubular core 5 as a core.

The hollow fiber membrane bundle 3 is formed by winding the hollow fibermembranes around the tubular core 5, fixing both ends of the hollowfiber membranes to the tubular housing body 21 by partition walls 8, 9,and cutting both ends of the hollow fiber membrane bundle 3. Both endsof the tubular core 5 with the hollow fiber membrane bundle 3 woundaround the outside surface thereof are fixed in a liquid-tight manner toboth end portions of the tubular housing body 21 by the partition walls8, 9, and the second blood chamber 12 as an annular space (tubularspace) is located between the outside surface of the tubular hollowfiber membranes and the inside surface of the tubular housing body 21.

The blood outflow port 25 formed at a side surface of the tubularhousing body 21 communicates with the second blood chamber 12. Thepartition walls 8, 9 are each preferably formed of a potting agent suchas polyurethane and silicone rubber.

In addition, the hollow fiber membrane bundle has intersection portions3 b where the hollow fiber membranes 3 a intersect in the vicinity ofthe center in the longitudinal direction of the tubular core 5. Theintersection portions (cross wind portions) 3 b are located differentlydepending on the portion of the hollow fiber membrane bundle. With theposition of the intersection portions thus varied, the intersectionportions in the overlapping layers do not overlap one another as shownin FIG. 1, whereby short-circuiting of the blood due to the overlappingof the intersection portions can be inhibited or prevented fromoccurring. The intersection portions are formed continuously by, forexample, a configuration in which two to six hollow fiber membraneswound substantially in parallel intersect alternately.

As the hollow fiber membranes, a porous gas exchange member is used. Asthe porous hollow fiver membrane, there can be used one which has aninside diameter of 100 to 1000 μm, a material thickness of 5 to 200 μm,preferably 10 to 100 μm, a porosity of 20% to 80%, preferably 30% to60%, and a pore diameter of 0.01 to 5 μm, preferably 0.01 to 1 μm.

As the material used for the porous film, a hydrophobic polymericmaterial such as polypropylene, polyethylene, polysulfone,polyacrynonitrile, polytetrafluoroethylene, cellulose acetate, etc. isused. Among these materials, polyolefin resin is a preferred material,and polypropylene is particularly preferred. It is more preferable touse a material whose wall is provided with micro-pores by an orientationmethod or a solid-liquid phase separation method.

The outside diameter (overall size) of the hollow fiber membrane bundle3 is preferably 30 to 162 mm, and the thickness of the hollow fibermembrane bundle 3 is preferably 3 to 28 mm.

As shown in FIGS. 3-5, a filter member 6 is provided on the outerperipheral portion 17 of the tubular hollow fiber membrane bundle 3. Thefilter member 6 has the function of trapping bubbles present in theblood flowing into the artificial lung 1 (tubular hollow fiber membranebundle 3).

In addition, like the tubular hollow fiber membrane bundle 3, the filtermember 6 is cylindrical in overall shape. With the filter member 6having such a shape, the inner peripheral portion (inner peripheralsurface) 61 if the filter member 6 is in contact with the outerperipheral portion (outer peripheral surface) 17 of the tubular hollowfiber membrane bundle 3. In addition, the filter member 6 is provided soas to cover substantially the whole part of the outer peripheral portion17 of the tubular hollow fiber membrane bundle 3.

With the filter member 6 thus provided, it is possible to enlarge thearea of the filter member 6 (inner peripheral portion 61) and,therefore, to trap the bubbles more assuredly. In addition, the largearea of the filter member 6 makes it possible to restrain or prevent theblood flow from being blocked, even upon generation of clogging (forexample, with a coagulated lump of blood) at a part of the filter member6.

As shown in FIG. 3, the second blood chamber 12 in the form of anannular gap is located between the filter member 6 and the housing 2.This makes it possible to prevent the filter member 6 from makingcontact with the inner peripheral surface of the housing 2, and toenable the blood flowing out from the outer peripheral portion 62 of thefilter member 6 to pass through the inside of the second blood chamber12 and, therefore, reach (flow into) the blood outflow port 25relatively assuredly.

In addition, the filter member 6 is preferably hydrophilic.Specifically, it is preferable that the filter member 6 itself is formedof a hydrophilic material or the surface of the filter member 6 issubjected to a hydrophilicity-imparting treatment (for example, plasmatreatment or the like). This helps ensure that the removal of bubbles atthe time of priming is easy to carry out, whereby it is more difficultfor the bubbles to pass when the blood with the bubbles mixed thereinpasses, and outflow of the bubbles from the filter member 6 can berestrained effectively.

The material constituting the filter member 6 is not particularlylimited. By way of example, a mesh-like material (screen filter) ispreferable as the constituent material. This makes it possible to trapthe bubbles more assuredly and to allow the blood to pass through thefilter member 6 relatively easily.

The size of the openings of the filter member 6 are not particularlylimited, although the openings are preferably not more than 50 μm, morepreferably in the range of 20 to 45 μm. This helps promote a relativelyreliable trapping of the bubbles.

The filter member 6 configured as above contributes to achievingrelatively reliable trapping of the bubbles present in the blood flowingfrom the first blood chamber 11 into the tubular hollow fiber membranebundle 3, so that the bubbles can be relatively securely prevented fromflowing out via the blood outflow port 25.

In addition, the bubbles trapped by the filter member 6 enter (flow)into the multiplicity of pores formed in the hollow fiber membranes 3 a(tubular hollow fiber membrane bundle 3) as the pressure at the bloodside is higher than inside the lumens of the hollow fiber membranebundle. The bubbles are thus discharged (flow out) from the gas outflowport 27 after passing through the lumens of the hollow fiber membranes 3a. As a result, the time taken for priming the bubbles can be shortened,and the bubbles can be prevented from stagnating in the tubular hollowfiber membrane bundle 3 (artificial lung 1). The filter member 6 neednot necessarily be so provided as to cover substantially the whole partof the outer peripheral portion 17 of the tubular hollow fiber membranebundle 3. For example, the filter member 6 may be so provided as tocover a part of the outer peripheral portion 17 of the tubular hollowfiber membrane bundle 3.

As shown in FIGS. 3-5, a heat exchanger unit is contained in the insideof the tubular core 5 of the artificial lung unit formed as mentionedabove. Various features pertaining to the heat exchanger unit will nowbe described.

The annular first blood chamber 11 is formed between the tubular core 5and the tubular heat exchanger unit, and the blood inflow port 24communicates with this blood chamber 11. As shown in FIGS. 3-5, thetubular heat exchanger unit includes a tubular heat exchange body 31, atubular heating medium chamber forming member 32 contained in the heatexchange body 31, and two tubular heat exchange body deformationrestraining portions 34, 35 inserted between the tubular heat exchangebody 31 and the tubular heating medium chamber forming member 32.

As the tubular heat exchange body 31, a so-called bellows type heatexchange body is used. As shown in FIG. 4, the bellows type heatexchange body 31 (bellows pipe) includes a bellows forming portionhaving a multiplicity of hollow annular projections formed substantiallyparallel to a central side surface thereof, and cylindrical portionsformed at both ends of the bellows forming portion and having an insidediameter approximately equal to that of the bellows forming portion. Oneof the cylindrical portions of the heat exchange body 31 is clampedbetween the inside surface of a side end portion of the blood inflowport 24 of the hollow tubular core 5 and a second header 23, and theother of the cylindrical portions of the heat exchange body 31 isclamped between the first header 22 and a tubular heat exchange bodyfixing member 49, which is inserted between a ring-like heat exchangebody fixing member 48 inserted in one end of the hollow tubular core 5and the first header 22.

The bellows type heat exchange body 31 is formed in a so-called minutebellows-like form, from a metal such as stainless steel, aluminum, etc.or a resin material such as polyethylene, polycarbonate, etc. A metalsuch as stainless steel and aluminum is preferably used, from theviewpoint of strength and heat exchange efficiency. Particularly, thebellows type heat exchange body 31 is composed of a bellows pipeassuming a wavy shape obtained by repetition of a multiplicity ofrecesses and projections substantially orthogonal to the axial direction(center axis) of the tubular heat exchange body 31.

As shown in FIGS. 3-5, the tubular heating medium chamber forming member32 is a tubular body opened at one end (on the side of the first header22), and includes a partition wall 32 a for partitioning the inside intoan inflow side heating medium chamber 41 and an outflow side heatingmedium chamber 42, a first opening 33 a communicated with the inflowside heating medium chamber 41 and extending in the axial direction, asecond opening 33 b communicated with the outflow side heat exchangechamber 42 and extending in the axial direction, and projections 36 aand 36 b. These projections 36 a, 36 b are diametrically opposed to eachother, are formed on the side surfaces at positions deviated by about90° from the first opening 33 a and the second opening 33 b, projectradially outwardly, and extend in the axial direction. The projection 36a enters into a groove formed at the center of the inside surface of theheat exchange body deformation restraining portion 34 and extends in theaxial direction to thereby restrain the heat exchange body deformationrestraining portion 34 from being moved. Similarly, the projection 36 benters into a groove formed at the center of the inside surface of theheat exchange body deformation restraining portion 35 and extends in theaxial direction, to thereby restrain the heat exchange body deformationrestraining portion 35 from being moved.

When the opening end side of the tubular heating medium chamber formingmember 32 is fitted in a heating medium chamber forming memberconnection portion 22 a of the first header 22 as shown in FIG. 4, apartition portion 22 b for bisecting the inside of the tubularconnection portion 22 a makes close contact with one surface (in thisembodiment, the lower surface) of a tip end portion of the partitionwall 32 a of the tubular heating medium chamber forming member 32. As aresult the inflow side heating medium chamber 41 in the tubular heatingmedium chamber forming member 32 is communicated with the heating mediuminflow port 28, and the outflow side heating medium chamber 42 iscommunicated with the heating medium outflow port 29.

In addition, the two heat exchange body deformation restraining portions34, 35 are provided at their abutting end portions with cutout portionsextending in the axial direction. When the two restraining portions 34,35 are assembled to abut against each other as shown in FIG. 5, a mediuminflow side passage 37 and a medium outflow side passage 38 are formed.It is to be understood that the two heat exchange body deformationrestraining portions 34, 35 may be formed as one body.

Now, the flow of the heating medium in the heat exchanger unit of theartificial lung 1 according to this embodiment will be describedreferring to FIGS. 3-5. The heating medium flowing into the inside ofthe artificial lung 1 via the heating medium inflow port 28 passesthrough the inside of the first header 22 to flow into the inflow sideheating medium chamber 41. Then, the heating medium passes through theinflow chamber side opening 33 a of the tubular heating medium chamberforming member 32, passes through the medium inflow side passage 37formed by the abutment portions of the heat exchange body deformationrestraining portions 34, 35, and flows between the heat exchange body 31and the heat exchange body deformation restraining portions 34, 35. Inthis instance, the heat exchange body 31 is warmed or cooled by theheating medium.

Then, the heating medium passes through the medium outflow side passage38 formed by the abutment portions of the heat exchange body deformationrestraining portions 34, 35, passes through the outflow chamber sideopening 33 b of the tubular heating medium chamber forming member 32,and flows out into the outflow side heating medium chamber 42 in thetubular heating medium chamber forming member 32. Subsequently, theheating medium passes through the inside of the first header 22 andflows out via the heating medium outflow port 29.

Now, the flow of blood in the artificial lung 1 will be described. Inthis artificial lung 1, the blood flowing into the artificial lung isdistributed via the blood inflow port 24 and flows into the blood guideportion 56 constituting a part of the first blood chamber 11 formedbetween the tubular core 5 and the tubular heat exchanger unit. Theblood flows between the tubular core 5 and the tubular heat exchangebody, then passes through the openings 52 located at a position opposedto the first blood guide portion 56, and flows out of the tubular core5.

The blood flowing out of the tubular core 5 flows into the plurality ofgrooves 51 on the outside surface of the tubular core 5 located betweenthe inside surface (inner peripheral portion 15) of the hollow fibermembrane bundle 3 and the tubular core 5, and then flows into the gapsin the hollow fiber membrane bundle 3. In the artificial lung 1, themultiplicity of grooves 51 are formed over substantially the wholeregion of the portion contributing to gas exchange of the hollow fibermembrane bundle 3 (the effective length or the portion not buried in thepartition wall), so that the blood can be dispersed to the whole part ofthe hollow fiber membrane bundle 3, the whole part of the hollow fibermembrane bundle can be utilized, and a relatively high gas exchangeperformance can be obtained.

Then, the blood makes contact with the hollow fiber membranes where gasexchange is performed, and then the blood flows into the second bloodchamber 12 formed between the tubular housing body 21 and the outsidesurface of the hollow fiber membranes (the outside surface of the hollowfiber membrane bundle 3). The bubbles present in the blood are trappedby the filter member 6, as described above, and eventually enters intothe lumens of the hollow fiber membranes 3 a.

The blood flowing into the second blood chamber 12 flows out of theartificial lung or is distributed via the blood outflow port 25. Inaddition, an oxygen-containing gas flowing in via the gas inflow port 26passes through the inside of the first header 22, flows via thepartition wall end face into the hollow fiber membranes, then passesthrough the inside of the second header 23, and flows out via the gasoutflow port 27.

Examples of the materials for forming the members other than the heatexchange body 31, i.e., the materials for forming the tubular housingbody 21, the tubular core 5, the first and second headers 22, 23 and thelike include polyolefins (e.g., polyethylene, polypropylene), esterresins (e.g., polyethylene terephthalate), styrene-based reins (e.g.,polystyrene, MS resin, MBS resin), and polycarbonates.

In addition, the blood contact surfaces in the artificial lung 1 arepreferably anti-thrombogenic surfaces. The anti-thrombogenic surfacescan be formed by covering the surfaces with an anti-thrombogenicmaterial and fixing the material. Examples of the antithrombogenicmaterial include heparin, urokinase, HEMA-St-HEMA copolymer, andpoly-HEMA.

FIG. 6 is a cross-sectional view of an artificial lung according to asecond embodiment of the present invention. The following description ofthe second embodiment will focus primarily on the differences betweenthis embodiment and the embodiment described above, with features in thesecond embodiment that correspond to those in the first embodiment beingidentified by the same reference numerals. A detailed discussion offeatures which have already been described will not be repeated inentirety.

This embodiment is the same as the first embodiment, except for theposition of the filter member. As shown in FIG. 6, the filter member 6is provided at an intermediate portion in the thickness (materialthickness) direction (the radial direction) of the tubular hollow fibermembrane bundle 3. Specifically, the filter member 6 is provided betweenan outside layer 18 and an inside layer 19 of the tubular hollow fibermembrane bundle 3.

In addition, an outer peripheral portion 62 and an inner peripheralportion 61 of the filter member 6 are in contact with the outside layer18 and the inside layer 19, respectively. Namely, the filter member 6 isclamped or situated between the outside layer 18 and the inside layer19.

The filter member 6 thus arranged makes it possible to relativelyreliably trap the bubbles present in the blood flowing from the firstblood chamber 11 into the tubular hollow fiber membrane bundle 3 and,hence, to securely prevent the bubbles from flowing out via the bloodoutflow port.

It is to be understood that the provision of one filter member 6 at anintermediate portion of the tubular hollow fiber membrane bundle 3 isnot limitative. For example, a plurality of filter members 6 may beprovided.

While the artificial lung according to the present invention has beendescribed above referring to the embodiments shown in the figures, theinvention is not limited to these embodiments, and the components of theartificial lung can be replaced by other members having the same orequivalent functions. In addition, components or features other thanthose described above can be utilized.

1. An artificial lung comprising: a housing; a hollow fiber membranebundle contained in said housing, said hollow fiber membrane bundlecomprising a multiplicity of gas exchanging hollow fiber membranes whichpossess lumens; a gas inflow portion and a gas outflow portion incommunication with each other through the lumens of said hollow fibermembranes; a blood inflow portion and a blood outflow portion in whichblood flows; said hollow fiber membrane bundle possessing a cylindricaloverall shape; and a bubble trapping filter member provided at an outerperipheral portion of said hollow fiber membrane bundle.
 2. Theartificial lung as set forth in claim 1, wherein said bubble trappingfilter member is in contact with an outer peripheral portion of saidhollow fiber membrane bundle and covers substantially the entirety ofsaid outer peripheral portion of said hollow fiber membrane bundle. 3.The artificial lung as set forth in claim 1, wherein a gap existsbetween said bubble trapping filter member and said housing.
 4. Theartificial lung as set forth in claim 1, wherein: said blood inflowportion has an inflow opening portion opening to an inner peripheralportion side of said hollow fiber membrane bundle, said blood outflowportion has an outflow opening portion opening to an outer peripheralportion side of said hollow fiber membrane bundle; and the blood passesfrom the inner peripheral portion side of said hollow fiber membranebundle to the outer peripheral portion side of said hollow fibermembrane bundle.
 5. The artificial lung as set forth in claim 1, whereinsaid filter member is hydrophilic.
 6. The artificial lung as set forthin claim 1, wherein said filter member is a mesh filter member.
 7. Theartificial lung as set forth in claim 6, wherein said mesh filter membercomprises openings of a size not more than 50 μm.
 8. An artificial lungcomprising: a housing comprising a blood inflow port through which bloodflows, a blood outflow port through which blood flows, a gas inflow portthrough which flows gas and a gas outflow through which flows gas; atubular hollow fiber membrane bundle positioned in the housing andcomprised of a plurality of hollow fiber membranes, said gas inflow portcommunicating with said hollow fiber membrane bundle and said gasoutflow port communicating with said hollow fiber membrane bundle; afirst annular blood chamber positioned radially inwardly of the hollowfiber membrane bundle and communicating with said blood inflow port; asecond annular blood chamber positioned radially outwardly of the hollowfiber membrane bundle and communicating with said blood outflow port;and an annular bubble trapping filter member positioned in the housingbetween a circumferential inner surface of the housing and the firstannular blood chamber to trap bubbles contained in blood in the hollowfiber membrane bundle.
 9. The artificial lung according to claim 8,comprising a heat exchanger unit positioned radially inwardly of thefirst annular blood chamber.
 10. The artificial lung according to claim8, wherein the second annular blood chamber is positioned between thecircumferential inner surface of the housing and the bubble trappingfilter member.
 11. The artificial lung according to claim 8, wherein theplurality of hollow fiber membranes are wound about a tubular core, anouter peripheral surface of said tubular core comprising a plurality ofannular grooves forming blood conduits through which blood flows. 12.The artificial lung according to claim 11, wherein blood in the firstannular blood chamber communicates with the plurality of annular groovesby way of openings formed in the tubular core.
 13. The artificial lungaccording to claim 12, wherein the openings are positioned diametricallyopposite the blood inflow port.
 14. The artificial lung according toclaim 8, wherein the tubular hollow fiber membrane bundle comprises aninner layer and an outer layer, said bubble trapping filter member beingpositioned between the inner layer and the outer layer of the tubularhollow fiber membrane bundle.
 15. The artificial lung according to claim8, wherein an inner peripheral surface of the bubble trapping filtermember is in contact with a outer peripheral surface of the tubularhollow fiber membrane bundle.
 16. The artificial lung as set forth inclaim 8, wherein said bubble trapping filter member is hydrophilic. 17.The artificial lung as set forth in claim 8, wherein said bubbletrapping filter member is a mesh filter member.
 18. The artificial lungas set forth in claim 17, wherein said mesh filter member comprisesopenings of a size not more than 50 μm.
 19. An artificial lungcomprising: a housing; a hollow fiber membrane bundle contained in saidhousing, said hollow fiber membrane bundle comprising an inner layer andan outer layer each comprised of a multiplicity of gas exchanging hollowfiber membranes which possess lumens; a gas inflow portion and a gasoutflow portion in communication with each other through the lumens ofsaid hollow fiber membranes; a blood inflow portion and a blood outflowportion in which blood flows; said hollow fiber membrane bundlepossessing a cylindrical overall shape; and a bubble trapping filtermember positioned between the inner layer and the outer layer of saidhollow fiber membrane bundle.